1. Field of the Invention
The invention relates to a coaxial connection for a printed circuit board comprising an essentially cylindrical adapter which is electrically connected to a first connector element with its first end and which is electrically connected to a second connector element with its second end whereby at least the first connector element is fastened to a printed circuit board.
2. Description of the Related Art
Printed circuit boards are brought into contact with one another under high frequency after assembly of the printed circuit board with SMD components and subsequent soldering. Precision of location and position of the SMD (surface mounted device) components has to be compensated hereby in radial and axial direction so that high-frequency characteristics are maintained. Up to now, cable sections were used for the above-mentioned electrical connection of two printed circuit boards whereby said cable sections were fastened to the printed circuit board with a connector at each end. The flexibility of the coaxial cable sections guaranteed compensation in precision of location and position of the SMD components. However, this type of connection is relatively expensive and has additionally the disadvantage that the space between two connected printed circuit boards is relatively large.
Known are coaxial connections for printed circuit boards which have an essentially cylindrical adapter that mates with a connector element with both of its ends, respectively. Such connectors allow a relatively small space between the two printed circuit boards connected to one another. Based on the elasticity of the adapter and the connector element, there is also a certain compensation possible in axial and radial direction. However, during such compensation there is stress applied onto the respective connector elements, which may lead to a break at the soldering joints. Such a break is especially possible when the printed circuit boards are subject to vibrations or jolts, or other unfavorable influences.
U.S. Pat. No. 4,925,403 discloses a coaxial connector between two printed circuit boards which are provided with an adapter having an outer and inner conductor. The inner conductor of the adapter is provided with a spring-loaded female connector, which respectively mates with a prong of a conductor of the printed circuit board. Minor lateral displacements of the printed circuit board are possible; however, these (lateral displacements) cause stress in the connection.
The object of the invention is to provide a coaxial connection for a printed circuit board of the above-mentioned type that avoids said disadvantages and which may nevertheless be manufactured relatively cost-effective and which is also operatively sound.
The object of the invention of a coaxial connection for a printed circuit board of this type is achieved according to claim 1. In the connection according to the invention, the adapter may be tilted at a relatively large range without a substantial buildup of stress. It is essential, based on the ball-and-socket joint, that the force of contact remains substantially constant during tilting of the adapter. The soldering joints are thereby stressed to a lesser degree than up to now and even on the inner conductor there are essentially no stress forces applied. The connection, according to the invention, makes possible a very compact design of a printed circuit board with a space (between one another) of five to ten millimeters, for example. Two printed circuit boards may be electrically connected to one another by ten connections, for example, whereby the tolerances that are created especially during soldering may be taken up essentially without application of forces.
Should the adapter be connected to the second connector element with its second end by means of a loose ball-and-socket joint according to a development of the invention, then relatively high axial tolerances may be taken up essentially without application of forces whereby the contact force remains substantially constant at the second end of the adapter as well.
According to a further development of the invention, the fixed ball-and-socket joint has interlocked joint parts that are detachable from each other. During assembly, the adapter may be locked onto the first connector element with its first end in the way of a snap fastener. This pre-assembly may be automated in a relatively simple and reliable manner.
The inner conductor of the adapter does not undergo any application of force especially when, according to a development of the invention, the two ends of the adapter are provided each with an electric contact surface in the shape of a ball section. The two ends of the adapter mate preferably with a sleeve-shaped part of a connection element. Thereby it is guaranteed in a special way that the inner conductor never undergoes any application of force and that the force of contact remains substantially constant.
According to a preferred embodiment, the fixed ball-and-socket joint is formed by the insulator of the adapter and the insulator of the first connector element. This provides for an especially favorable and durable snap-on connection between two joint elements. The connection of the first ball-and-socket joint may be disconnected repeatedly without problems and without damage thereto.
Additional advantageous characteristics can be seen in the subordinate patent claims and the following descriptions and multiple drawings.
Two embodiment examples of the invention are explained below in more detail with the aid of accompanying drawings.